Drug information of Digoxin

Digoxin

Drug group:

Digoxin is derived from the leaves of a digitalis plant. Digoxin helps make the heart beat stronger and with a more regular rhythm. Digoxin is used to treat heart failure .
Digoxin is also used to treat atrial fibrillation , a heart rhythm disorder of the atria (the upper chambers of the heart that allow blood to flow into the heart).

Mechanism of effect

Digoxin inhibits the Na-K-ATPase membrane pump, resulting in an increase in intracellular sodium. The sodium calcium exchanger (NCX) in turn tries to extrude the sodium and in so doing, pumps in more calcium.
Increased intracellular concentrations of calcium may promote activation of contractile proteins (e.g., actin, myosin). Digoxin also acts on the electrical activity of the heart, increasing the slope of phase 4 depolarization, shortening the action potential duration, and decreasing the maximal diastolic potential.

Pharmacodynamic

Digoxin , a cardiac glycoside similar to digitoxin, is used to treat congestive heart failure and supraventricular arrhythmias due to re-entry mechanisms, and to control ventricular rate in the treatment of chronic atrial fibrillation.

Pharmacokinetics

Bioavailability: 60-80 % (tablet); 70-85% (elixir)
Onset: 0.5-2 hr (PO) for initial effect and 2-6 hr for maximal effect; 5-30 min (IV) for initial
effect and 1.5-4 hr for maximal effect
Duration: 3-4 days
Peak serum time: 1-3 hr (PO)
Distribution
Protein bound: 20-25%
Vd: 6-7 L/kg
Metabolism
Metabolized by liver
Metabolites: Digoxigeninbisdigitoxoside, digoxigeninmonodigitoxoside (active)
Elimination
Half-life: 1-3 days
Excretion: Urine (57-80%), feces (9-13%; includes bile)

Drug indications

Congestive Heart Failure

Dosage

Atrial Fibrillation
Rapid digitalizing (loading-dose) regimen
• IV: 8-12 mcg/kg (0.008-0.012 mg/kg) total loading dose; administer 50% initially; then may cautiously give 1/4 the loading dose q6-8hr twice; perform careful assessment of clinical response and toxicity before each dose .
• PO: 10-15 mcg/kg total loading dose; administer 50% initially; then may cautiously give 1/4 the loading dose q6-8hr twice; peform careful assessment of clinical response and toxicity before each dose .
Maintenance
• PO: 3.4-5.1 mcg/kg/day or 0.125-0.5 mg/day PO; may increase dose every 2 weeks based on clinical response, serum drug levels, and toxicity .
• IV/IM: 0.1-0.4 mg qDay; IM route not preferred due to severe injection site reaction
Heart Failure
As per ACCF/AHA guidelines, a loading dose to initiate digoxin therapy in patients with heart failure is not necessary .
0.125-0.25 mg PO/IV qDay; higher doses including 0.375-0.5 mg/day rarely needed

Drug contraindications

hypersensitivity to this drug

Alerts

• Use caution in chronic constrictive pericarditis, electrical cardioversion, severe bradycardia, severe heart failure, severe pulmonary disease, sick sinus syndrome, ventricular tachycardia, ventricular premature contractions, Wolff-Parkinson-White syndrome, electrolyte imbalance, hypothyroidism or hyperthyroidism, hypoxia, idiopathic hypertrophic subaortic stenosis, renal disease, concomitant diuretics or steroid medicine .
• Use caution in patients with acute myocardial infarction .
• Avoid rapid IV administration in digitalized patients; may produce serious arrhythmias

Points of recommendation

• Try to take the medication at the same time every day.
• Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.
• While using digoxin , you may need frequent blood tests. Your kidney function may also need to be checked.
• Use digoxin regularly even if you feel fine or have no symptoms. Get your prescription refilled before you run out of medicine completely.
• You should not stop using digoxin suddenly. Stopping suddenly may make your condition worse.
• IM administration is not recommended due to associated pain and muscle necrosis. If IM administration is required, no more than 500 mcg of the injectable formulation should be injected into a single site.

Pregnancy level

C


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